A can do a work in 24 days, B can do the same work in 18 days, and C can do it in 12 days. If they work together, how long will it take to complete the work?
Answer: C. 6 days
The combined work rate is 1/24 + 1/18 + 1/12 = 1/4. Therefore, they will complete the work in 4 days.